Things That Won't Work
- Git (GitLab) - this requires 4GB between RAM and swap which is simply too much for all models up to the Raspberry Pi 3B+. GitLab is basically a self-hostable GitHub.
- Forum (Discourse) - this is borderline because it requires 1GB+ RAM with additional swap space, so at the very least it would be the only thing that you installed. Discourse is a modern forum which "takes security seriously". (It can be browsed without JS; super annoying infinite scroll with JS.)